diff --git a/README.md b/README.md
index ac78191..5096015 100644
--- a/README.md
+++ b/README.md
@@ -107,6 +107,8 @@ tmux attach -t my-agent
 | `pluk patterns --cli=claude` | Show loaded patterns for a CLI |
 | `pluk <command> --help` / `-h` | Show usage (works after any subcommand) |
 
+Unknown or misspelled `--flags` on any command exit 2 (`unknown flag --name`) instead of being silently ignored.
+
 ### Attach Flags
 
 | Flag | What it does |
diff --git a/changelog.d/fixed-346.md b/changelog.d/fixed-346.md
new file mode 100644
index 0000000..764ce18
--- /dev/null
+++ b/changelog.d/fixed-346.md
@@ -0,0 +1 @@
+- `pluk` now rejects unknown or misspelled `--flags` (e.g. `--captur=50`, `--entr`) with an error (exit 2) instead of silently ignoring them.
diff --git a/src/cli.ts b/src/cli.ts
index 07ab9db..6c932f0 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -69,6 +69,17 @@ const BOOL_FLAGS = new Set([
   'no-open', 'dangerous', 'json', 'enter', 'literal',
 ]);
 
+const KNOWN_FLAGS = new Set([
+  'help', ...VALUE_FLAGS, ...BOOL_FLAGS, 'capture', 'diagnostics',
+]);
+
+function rejectUnknownFlag(name: string): void {
+  if (!KNOWN_FLAGS.has(name)) {
+    console.error(`${paintStderr(ANSI_RED, 'Error:')} unknown flag --${name} (see pluk --help)`);
+    process.exit(2);
+  }
+}
+
 function parseArgs(args: string[]): { positional: string[]; flags: Record<string, string> } {
   const positional: string[] = [];
   const flags: Record<string, string> = {};
@@ -79,6 +90,7 @@ function parseArgs(args: string[]): { positional: string[]; flags: Record<string
       if (eqIdx > 0) {
         const name = arg.slice(2, eqIdx);
         const value = arg.slice(eqIdx + 1);
+        rejectUnknownFlag(name);
         if (BOOL_FLAGS.has(name) && value !== 'true' && value !== 'false') {
           console.error(`${paintStderr(ANSI_RED, 'Error:')} --${name} is a boolean flag: use --${name} or --${name}=false`);
           process.exit(2);
@@ -86,6 +98,7 @@ function parseArgs(args: string[]): { positional: string[]; flags: Record<string
         flags[name] = value;
       } else {
         const name = arg.slice(2);
+        rejectUnknownFlag(name);
         if (VALUE_FLAGS.has(name)) {
           console.error(`${paintStderr(ANSI_RED, 'Error:')} --${name} requires a value: use --${name}=<value>`);
           process.exit(2);
diff --git a/test/cli-error-paths.test.js b/test/cli-error-paths.test.js
index 5e50b9a..f544e99 100644
--- a/test/cli-error-paths.test.js
+++ b/test/cli-error-paths.test.js
@@ -346,3 +346,16 @@ test('bare boolean switches are still accepted', () => {
   assert.equal(r.status, 0);
   assert.doesNotMatch(r.stderr, /requires a value/);
 });
+
+test('unknown or misspelled --flags exit 2 with an unknown-flag error', () => {
+  for (const [args, flag] of [
+    [['watch', 's', '--captur=50'], 'captur'],
+    [['send', 's', '--text=hi', '--entr'], 'entr'],
+    [['watch', 's', '--'], ''],
+    [['watch', 's', '--=x'], ''],
+  ]) {
+    const r = spawnSync(process.execPath, [CLI, ...args], { encoding: 'utf8' });
+    assert.equal(r.status, 2, args.join(' '));
+    assert.match(r.stderr, new RegExp(`unknown flag --${flag}`));
+  }
+});